1. Field of the Invention
The present invention relates generally to the field of ophthalmics, more particularly to intraocular lenses (IOLs), and still more particularly to instruments for implanting IOLs in eyes.
2. Background Discussion
It may helpful to the understanding of the present invention to define the terms "phakic" and "aphakic" as relates to human eyes. The term "phakic" applies to eyes in which the natural ocular lens is still present. This is in contrast to "aphakic" that applies to eyes from which the natural lens has--for any reason--been removed.
A phakic eye is considered a dynamic or active eye because the living, natural lens is subject to change over time. In contrast, an aphakic eye is considered a static eye because the natural ocular lens has been removed. Vision in a normal eye is enabled by light from a viewed image being refracted to the retina by the cornea and the natural lens located between the cornea and the retina.
A relatively common ocular problem is impaired or complete loss of vision due to the natural lens becoming cloudy or opaque--a condition known as cataract. The formation of cataracts is typically associated with natural bodily aging, for example, due to prolonged exposure to ultraviolet light, and most individuals over the age of about 60 years suffer from cataracts at least to some extent.
So far as is known, cataracts cannot currently be cured, reversed, or even significantly arrested. Accordingly, corrective action for serious cataracts involves surgically removing the natural lens when the lens becomes so cloudy that vision is substantially impaired. The result is that a phakic eye then becomes an aphakic eye.
After a defective natural lens has been surgically removed, the current (since about the 1940's) vision-restoring procedure is to implant in the aphakic eye an artificial, refractive replacement lens called an intraocular lens (IOL) having an optic and optic fixation means. Previously (and in some cases, still), thick, heavy, high diopter spectacles were prescribed for aphakic eyes. Such spectacles however were and still are generally disliked by most aphakic individuals for their weight and unsightly appearance.
Until relatively recently, IOLs for aphakic eyes were typically made from rigid polymethyl methacrylate (PMMA), a hard, biocompatible, plastic material. Within the past few years, however, the manufacture of IOL's has largely shifted from rigid PMMA to soft, elastically deformable silicone or acrylic material that enables insertion of folded (or otherwise dimensionally-reduced) IOLs through substantially smaller ocular incisions that those required for the implanting of rigid IOL's. Such smaller ocular incisions typically minimize patient trauma, reduce the risk of surgical complications and speed post-surgical recovery.
In addition to continuing interest in implanting IOL's in aphakic eyes, attention has recently been given to the implanting of IOL's in otherwise healthy phakic eyes to correct such common vision problems as myopia, hyperopia, presbyopia and astigmatism.
This implanting of corrective IOLs in phakic eyes is an often-attractive alternative to the wearing of corrective spectacles or contact lenses, which limit certain activities and even certain professions, or having performed such ocular surgical procedures on the cornea as radial keratomy (RK), photo-radial keratectomy (PRK) or LASIK, which may not be desired by or contra-indicated for some individuals.
In fact, the implanting of corrective IOLs in phakic eyes to correct vision problems is considered by many in the field of ophthalmics to be one of the remaining frontiers of vision correction.
Although aphakic IOL's are almost always implanted in the posterior chamber of the eye from which the natural lens has been removed, corrective IOL's for phakic eyes are usually implanted in the anterior chamber of the eye between the cornea and the iris.
The small anterior chamber axial dimension--typically only about 2 mm--between the posterior (rear) surface of the cornea and the anterior (front) surface of the iris, requires that anterior chamber IOL's typically be very thin to avoid undesirable contact with the easily-damaged endothelial layer of the cornea.
Elastically deformable IOL's are introduced into the eye, in this case, the anterior chamber of the eye, through some type of small injector nozzle in which the IOL's are folded or deformed to pass through and out of the nozzle after the nozzle has been inserted through a small ocular incision. As the deformed IOL'S are pushed out of the nozzle tip, they elastically unfold, typically, in an uncontrolled manner, to regain their original optical shape. However, uncontrolled unfolding of IOL's in the anterior chamber creates a serious risk of the IOL's contacting and injuring the sensitive endothelial surface of the cornea, thereby possibly causing a new vision problem.
Accordingly, a principal objective of the present invention is to provide an IOL implanting (insertion) instrument that provides precisely controlled unfolding of an elastically deformed IOL after the IOL has been introduced into an eye, particularly, the anterior chamber of an eye. It will be appreciated, however, that the IOL implanting instrument can also be used for the implanting of an elastically deformable IOL in the posterior chamber of an eye.